# Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility

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## Abstract

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## Simple Summary

## Abstract

^{3}/h (1.77 ft

^{3}/min) per hen resulting in 7092 m

^{3}/h (4174 ft

^{3}/min) for the 2365 birds, which falls at the higher end of the desired cold weather (0 °C) ventilation range. Contours of airflow, temperature, and pressure were generated to visualize results. Three two-dimensional planes were created at representative cross-sections to evaluate the contours inside and outside the barn. Five animal-occupied zones within each of the model planes were evaluated for practical hen comfort attributes. The simulation output suggested the TISE standard ventilation system could limit air speed to a comfortable average of 0.26 m/s (51 ft/min) and the temperature could be maintained between 18 and 24 °C on average at the bird level. Additionally, the indoor static pressure difference was very uniform averaging −25 Pascal (0.1 inches of water), which falls in the normal range for a floor-raised hen house with negative-pressure ventilation during cold weather conditions. Findings confirmed that CFD modeling can be a powerful tool for studying ventilation system performance at the bird level, particularly when individual animals are modeled, to assure a comfortable indoor environment for animal welfare in poultry facilities.

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Development of the CFD Model

#### 2.1.1. The Study Poultry House

^{2}/bird (1.2 ft

^{2}/bird). Colony nesting boxes were located at the barn centerline with a total square footage of 232.26 m

^{2}(2500 ft

^{2}) and included 250 compartments (1.67 × 4 ft).

#### 2.1.2. Two- and Three-Dimensional Computational Domains

#### 2.1.3. Modeling the Birds

^{2}(1.24 ft

^{2}), which was equivalent to a hen body weight of approximately 1.6 kg (3.5 lb) based on the relationship between body weight (M) and surface area (S) (Equation (1) [25]). In addition, an estimated distance between birds was calculated based on the stocking density by assuming all the birds were evenly distributed; note that this condition was fairly well reflected in Figure 1. In total, 2365 hens were modeled, which is approximately one-eighth of the total birds housed. The distance between the bottom of a single bird and the ground was 7 cm (2.76 in.) [26]. The side-to-side distance between two adjacent birds was 15 cm (6 in.), and the distance from the back of a bird to the front of the neighboring bird was 11 cm (4.4 in.) (Figure 6).

#### 2.2. Boundary Conditions

- Wall: The ground, ceiling, roof, slatted floor, nest boxes, litter area, inlet baffles, sidewalls, animal surfaces, and the top surface of the computational domain were defined as wall boundary conditions. Note that all “walls” were defined as non-slip walls except for the top surface of the computational domain which was defined as a zero-shear stress wall with no resistance along the surface.
- Body heat: Each hen model was defined as a solid volume, whose surface was defined as solid wall with a constant typical hen body temperature of 42 °C (107.6 °F). A heat generation rate of 4467 W/m
^{3}was assigned to the outer hen surfaces [23]. - Symmetry: This boundary condition was used where the physical geometry of interest and the expected pattern of the flow/thermal solution had mirror symmetry, which included the front and back surfaces of the computational domain along the z-axis and both near and far ends of the house, as those surfaces represented internal faces that accounted for one-eighth of the actual scenario.
- Wind velocity: The left surface of the computational domain was defined as a boundary condition of “velocity inlet” with a specified wind speed of 2.0 m/s (393.7 ft/min) traveling along the positive x-axis (Figure 2). Wind velocity profile was constant with elevation.
- Pressure outlet: The right surface of the computational domain was assigned a boundary condition of “pressure outlet” through which flow exits to atmospheric pressure.
- Atmosphere: For this study, the temperature of the atmosphere was specified as 0 °C (32 °F) at zero-gauge pressure.
- Interior: Two faces of each inlet perpendicular to the wind direction were assigned boundary conditions of “interior.” This allowed those “surfaces” to be open faces to represent a portion of the computational domain through which air could flow. Additionally, the exhaust fan had two faces defined as interior through which air would flow.
- Driving force 3D fan zone: The volume of the exhaust fan was defined as a “3D fan zone” where the entire fan volume was considered a fluid cell zone, which simulated the effect of an axial fan by applying a distributed momentum source. In addition, the fan was defined with a hub radius of 5 cm (2 in.), a tip radius of 46 cm (18 in.), and a thickness of 5 cm (2 in.). Rotational speed was specified as 60 radian/s (573 rpm). A constant pressure-jump of 18 Pascal (0.072 inches of water) was applied across all the cells in the fan zone in order to assure the desired hen ventilation rate [24] would fall in a reasonable range for the actual situation (cold weather and hen density). This pressure-drop value along with other inputs of the exhaust fan, comprised the “3D fan zone”, which was set to drive the entire flow regime.

#### 2.3. Mesh Settings

#### 2.4. Solver Settings

#### 2.5. Data Visualization

#### 2.6. Ventilation Rate

^{3}/h/hen (0.35 and 1.75 ft

^{3}/min [cfm]/hen) [29]. The simulation used a rate of 2.99 m

^{3}/h per hen (1.77 cfm/hen), on the high end of recommended cold weather ventilation rate, for evaluation at 0 °C. This resulted in a total ventilation rate of about 7092 m

^{3}/h (4174 cfm) for the study hen house section with 2365 hens. All inlets modeled in this study had 3.81-cm (1.5 in.) tall openings to provide a suitable static pressure difference [30] at this ventilation rate.

#### 2.7. Evaluation Criteria

#### 2.8. Statistical Analysis

- H
_{0}: There was no difference in the means of factor Plane. - H
_{0}: There was no difference in the means of factor Zone. - H
_{0}: There was no interaction between factors Plane and Zone.

## 3. Results

#### 3.1. Air Velocity Analysis

#### 3.2. Temperature Analysis

#### 3.3. Pressure Analysis

#### 3.4. Animal Zone Analysis

#### 3.5. Verification and Validation

## 4. Discussion

^{3}/h (4174 ft

^{3}/min) for the study hen house, which met the demands for 2365 hens during minimum ventilation in cold weather [29]. This ventilation rate was on the higher end of recommended air exchange range for hens during cold weather (3.0 m

^{3}/h or 1.77 ft

^{3}/min per hen), which was appropriate for the evaluation at 0 °C. The egg-laying flock was modeled as heated, hen-shaped individuals evenly distributed throughout the building [25,26], which is an improvement over using a heated cube to represent each group of caged hens, as in [24].

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Pictures of the study hen house. (

**a**) Interior view, (

**b**) close-up view of a ceiling inlet, (

**c**) close-up view of a sidewall exhaust fan.

**Figure 5.**A single hen model with simplified geometry from various views: (

**a**) Isometric, (

**b**) top, (

**c**) back, (

**d**) right side.

**Figure 7.**Data visualization. (

**a**) Three designated two-dimensional planes based on the ventilation feature within each where “I” stands for “inlet”, “N” stands for “no-ventilation features”, and “F” is short for “exhaust fan”; (

**b**) five zones in house cross-section that represent areas at hen level.

**Figure 8.**The contour of air velocity magnitudes at three planes with a legend of colors ranging from 0 to 5 m/s. Plane I with inlets, Plane N with no ventilation features, and Plane F with exhaust fan.

**Figure 9.**Isometric view of house showing the location of three selected planes and overall airflow patterns and air velocity magnitudes inside the hen house with inlets at the top of both sidewalls and sidewall exhaust fan. Plane I with inlets, Plane N with no ventilation features, and Plane F with exhaust fan.

**Figure 10.**Indoor air velocity vectors at three planes with corresponding ventilation features (inlets and fan). Plane I with inlets, Plane N with no ventilation features, and Plane F with exhaust fan.

**Figure 11.**The contour of temperatures at three planes. Plane I with inlets, Plane N with no ventilation features, and Plane F with exhaust fan.

**Figure 12.**Indoor temperature contours at three planes. Plane I with inlets, Plane N with no ventilation features, Plane F with exhaust fan.

**Figure 13.**Simulation outputs of environment parameters from five zones at three planes: (

**a**) Air speed, (

**b**) temperature, (

**c**) pressure. Error bars indicate standard deviations while cross bars indicate no statistically significant differences at 95% family-wise confidence level. Plane I with inlets, Plane N with no ventilation features, Plane F with exhaust fan.

**Table 1.**Analysis of variance (ANOVA) of air speed, air temperature, and pressure from five animal zones at three planes.

Parameter | Factor | df | Pr (>F) |
---|---|---|---|

Air speed | Plane | 2 | <2.2 × 10^{−16} |

Zone | 4 | <2.2 × 10^{−16} | |

Plane × Zone | 8 | <2.2 × 10^{−16} | |

Residuals | 25,856 | ||

Temperature | Plane | 2 | <2.2 × 10^{−16} |

Zone | 4 | <2.2 × 10^{−16} | |

Plane × Zone | 8 | <2.2 × 10^{−16} | |

Residuals | 25,856 | ||

Pressure | Plane | 2 | <2.2 × 10^{−16} |

Zone | 4 | <2.2 × 10^{−16} | |

Plane x Zone | 8 | <2.2 × 10^{−16} | |

Residuals | 25,856 |

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**MDPI and ACS Style**

Chen, L.; Fabian-Wheeler, E.E.; Cimbala, J.M.; Hofstetter, D.; Patterson, P.
Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility. *Animals* **2020**, *10*, 1067.
https://doi.org/10.3390/ani10061067

**AMA Style**

Chen L, Fabian-Wheeler EE, Cimbala JM, Hofstetter D, Patterson P.
Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility. *Animals*. 2020; 10(6):1067.
https://doi.org/10.3390/ani10061067

**Chicago/Turabian Style**

Chen, Long, Eileen E. Fabian-Wheeler, John M. Cimbala, Daniel Hofstetter, and Paul Patterson.
2020. "Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility" *Animals* 10, no. 6: 1067.
https://doi.org/10.3390/ani10061067